The present invention relates to a cylinder for an internal combustion engine of a manually guided implement, as well as a method for producing such a cylinder.
Manually guided implements, such as chain saws, brush cutters or the like, are equipped for the drive means with a small, single-cylinder internal combustion engine. To achieve an adequate drive capacity the internal combustion engine is operated at high speeds. When embodied as a two-cycle engine, a clean gas distribution is necessary in particular in the region of one or more transfer channels that are provided therefor. A suitable gas distribution is in this connection brought about in particular by a streamlined configuration of the transfer channel.
Relative to the piston displacement of the internal combustion engine, a high output is achieved at high speeds. The material stressing is correspondingly pronounced. An adequately sturdy internal combustion engine for receiving the thermal and mechanical output is, under the conditions of a mass production, to be produced with simple means. In particular, in this connection the manufacture of suitably formed transfer channels is to be taken into account.
Known from AT 393 409 B is a cast cylinder of a two-cycle engine, the cast cylinder body of which is provided with transfer channels that are open inwardly into a cylinder chamber. A second, similarly cast cylinder component is provided for being pressed into the cylinder body. The second cylinder component is provided on the outer side with projecting shaped parts that in the mounted state extend into the transfer channels and for the production of a suitable gas distribution form a curved, inwardly directed transfer channel. At its upper edge, the second cylinder component is provided with recesses that together with associated recesses of the cylinder body form a transfer window. In the mounted state, there results a butt joint between two components that extends approximately in the middle of the transfer window and is interrupted by the transfer window. After the pressing together of the two components, a common coating is provided on the inner side.
During the pressing of the second cylinder component into the cylinder body, a precise orientation of the position of the two parts relative to one another is necessary. Small errors in the angle in the circumferential direction lead to a non-alignment of the two components when forming the transfer channel. During the pressing-in, damage can occur to the two parts. A pressing-in at the wrong angle adversely affects the flow guidance of the fuel/air mixture in the transfer channels.
The cast component that is to be pressed in, as well as the cast cylinder body, are relatively brittle. To achieve the provided press fit, it is necessary to maintain low tolerances. High operating stresses and thermal deformations can adversely affect the press-fit connection. It is not possible to exclude damage to the coating in the region of the joint.
It is therefore an object of the present invention to improve the cylinder for the internal combustion engine of a manually guided implement such that a reliable operation is made possible under high operating loads with a simple manufacture.
It is a further object of the present invention to provide a simplified method for producing such a cylinder.